Apparatus for packaging semiconductor device and method for packaging the same

ABSTRACT

An apparatus for packaging a semiconductor device and a method for packaging the same. The apparatus includes a closed printing chamber having a baseplate on the bottom of the closed printing chamber. A pressure controlling system is connected to the closed printing chamber. The baseplate includes a heating unit. A paste source tank is located in the closed printing chamber.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwanapplication serial no. 87121967, filed Dec. 31, 1998, the fulldisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an apparatus and a method forpackaging a semiconductor device. More particularly, the presentinvention relates to an apparatus and an improved method for a glob toppackaging process.

[0004] 2. Description of the Related Art

[0005] A liquid encapsulant and dam materials are used in variouspackaging technologies in a dispensing process. This process is widelyused in chip-on-board (COB), flip chip (FC), ball grid array (BGA), chipscale package (CSP) and multi-chip module (MCM).

[0006] The dispensing process has to apply dam materials on the edge ofa desired encapsulation area and a low-viscosity encapsulant material isapplied on the top of the chip. The dispensing process is sequentialprocesses, in which first the dam materials and then the encapsulationmaterial are applied on each chip, one by one, to complete the process.

[0007] The current dispensing process has a low throughput and voids.Because the current process is performed at atmospheric pressure, air iseasily mixed into the encapsulation material, and, as a result, voidsare easily formed in the packages. These voids are decrease thereliability of the packages. Additionally, because the technology issplit into two steps, it is difficult to increase the throughput.Moreover, the dam material increases manufacturing costs.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention provides an apparatus and amethod for packaging a semiconductor device that increases thereliability and the throughput of packages, and decreases manufacturingcosts.

[0009] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, theinvention provides an apparatus for packaging a semiconductor device.The apparatus includes a closed printing chamber having a baseplate onthe bottom of the closed printing chamber. A pressure controlling systemis connected to the closed printing chamber. The baseplate includes aheating unit. A paste source tank is located in the closed printingchamber.

[0010] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, theinvention provides a method for packaging a semiconductor device. Themethod includes the following steps. A baseplate located on the bottomof a closed printing chamber is provided. A device and a stencil havinga mesh are mounted on the baseplate. The device is located within themesh. An amount of preheated paste is placed on the stencil. A pressureof the closed printing chamber is adjusted to a first pressure. Aprinting step is performed to fill the mesh with the paste and cover thedevice. The pressure of the closed printing chamber is adjusted to asecond pressure to remove voids trapped in the plugs. The pressure ofthe closed printing chamber is adjusted to a third pressure. A scrapingstep is performed to remove the redundant paste.

[0011] In the invention, the encapsulation area is defined by a mesh sothat there is no need for the dam material. The process is performed inone step. The throughput is increased and the manufacturing costs aredecreased. Because the process is performed in a vacuum, the problem ofvoids is avoided and the packages are more reliable.

[0012] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

[0014]FIG. 1 is a schematic diagram showing an apparatus formanufacturing a plug according to the invention;

[0015]FIGS. 2A through 2E are schematic, cross-sectional views showingthe process steps according to the invention for manufacturing a plug;and

[0016]FIG. 3 is a schematic diagram showing the relationship betweentime and pressure in the manufacturing process of FIGS. 2A through 2Eaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

[0018]FIG. 1 is a schematic diagram showing an apparatus formanufacturing a plug according to the invention.

[0019] Referring to FIG. 1, a closed printing chamber 10 is provided.The closed printing chamber 10 is an operation region in which a printedcircuit board is printed. The closed printing chamber 10 is connected toa pressure control system 12 which controls the pressure in the closedprinting chamber 10. A baseplate 14 having a heating unit 16 is locatedon the bottom of the closed printing chamber 10. The baseplate 14 isused as a mounting surface for a printed circuit board. The heating unit16 is used for heating the paste on the printed circuit board mounted onthe baseplate 14 during a printing step. A paste source tank 18 forproviding paste is located inside the closed printing chamber 10. Aheating unit located near an outlet opening 20 of the paste source tank18 is used for heating the paste to reduce its viscosity.

[0020]FIGS. 2A through 2E are schematic, cross-sectional views showingthe process steps according to the invention for manufacturing a plug.

[0021] Referring to FIG. 2A, chips 32 are attached to carriers 34respectively by a material 36 such as epoxy or conducting paste. Thechips 32 are electrically coupled to the carriers 34 by conducting wires38. The carriers 34 include a printed circuit board or a ball grid arraysubstrate. In the embodiment, the carriers 34 are ball grid arraysubstrates. The step of coupling the chips 32 and the carriers 34includes wire bonding, tape automatic bonding or flip chip. The chips 32and the carriers 34 are placed on a baseplate 14 located in a closedprinting chamber (as reference numeral 10 shown in FIG. 1). A stencil 30is placed on the base plate 14, and the chips 32 and the carriers 34 arelocated within a mesh 40 of the stencil 30. An amount of a preheatedpaste 42 is placed on the stencil 30. A preferred amount of the paste 42is sufficient for one or two performances of a printing step. The paste42 is preheated to a temperature of about 40 to 90° C. before it isapplied on the stencil 30. The closed printing chamber is pumped down toabout 0.01 to 5 Torr, and then a printing step is performed. The paste42 is heated to a temperature of about 50 to 120° C. by the heating unitof the baseplate 14 (as reference numeral 16 shown in FIG. 1) during theprinting step. A squeegee 44 is used to print the paste 42. The paste 42fills the mesh 40 and covers the chips 32 and the carriers 34.

[0022] The purpose of preheating the paste 42 is to reduce the viscosityof the paste 42. The purpose of heating the paste 42 during the printingstep is the same. The heating temperature depends on the material of thepaste 64, and it should be just sufficient to reduce the viscosity butnot high enough to cause thermally cure the paste 42. Thus, a constantviscosity of the paste 42 is maintained for each printing step.

[0023] In the invention, the encapsulation area of the chips 32 isdefined by the mesh 40, not the dam material. The manufacturing costsare decreased. Additionally, since a plurality of chips is placed in onemesh, the throughput is increased. Further, one chip in one mesh is alsosuitable.

[0024] Referring to FIG. 2B, bubbles 46 are formed because of theviscosity of the paste 42 or the flow of the paste 42. To make sure thebubbles 46 are completely removed, the closed printing chamber ispressurized with air to about 350 to 1000 Torr so as to introduce apositive pressure. Thus, the bubbles 46 are moved to the surface of thepaste 42 and broken due to the positive pressure. The positive pressurealso helps to densify the paste 42. The process mentioned above issuitable for a low viscous paste whose viscosity is about 200 to 300Pa·s.

[0025] For very high viscous paste 42 whose viscosity is about 600 to1000 Pa·s, the positive pressure is about 0.5 to 2.0 Kg/cm² to makeremoval of the bubbles 46 trapped in the paste 42 more efficient.Furthermore, if necessary, the period of time for which the positivepressure is applied can be increased to eliminate the bubbles 46.

[0026] Referring to FIG. 2C, the closed printing chamber is pumped downto about 5 to 20 Torr. The squeegee 44 is used to scrape the paste 42.Thus, the redundant paste 42 is removed and the surface uniformity ofthe paste 42a is improved.

[0027] Referring to FIG. 2D, the stencil 30 is removed and the closedprinting chamber is returned to atmospheric pressure.

[0028] Referring to FIG. 2E, the paste 42 a is cured and tin balls aresoldered onto the carriers 34, the individual packages are split apart.Thus, each package 50 includes a chip 32 and a carrier 34.

[0029]FIG. 3 is a schematic diagram showing the relationship betweentime and pressure in the manufacture process illustrated in FIGS. 2Athrough 2E according to the invention.

[0030] Referring to FIG. 3, the closed printing chamber is pumped downto about 0.01 to 5 Torr (reference numeral 70 shown in FIG. 3), and theprinting step is performed. To make sure the bubbles trapped in the plugare completely removed to densify the paste, the closed printing chamberis pressurized with air to about 350 to 1000 Torr (reference numeral 72shown in FIG. 3) to introduce a positive pressure. Thus, the bubbles areforced to the surface of the plug and broken due to the positivepressure. The closed printing chamber is pumped down to about 5 to 20Torr (reference numeral 76 shown in FIG. 3). The squeegee is used toremove the redundant paste and ensure the surface uniformity of theplug. The process mentioned above is suitable for a low viscous pastewhose viscosity is about 200 to 300 Pa·s.

[0031] For very high viscous paste whose viscosity is about 600 to 1000Pa·s, the positive pressure is applied to about 0.5 to 2.0 Kg/cm²(reference numeral 74 shown in FIG. 4) so that the removal of thebubbles trapped in the plug is more efficient. The printing chamber isthen pumped down to about 5 to 20 Torr (reference numeral 78 shown inFIG. 4). The squeegee is used to remove the redundant paste and ensurethe surface uniformity of the plug.

[0032] According to the foregoing, the advantages of the inventioninclude the following:

[0033] 1. The present invention provides an apparatus for packaging asemiconductor device that is operated under a vacuum so that the problemof forming voids in the packages is avoided and the reliability of thepackages is improved.

[0034] 2. In the invention, the method for packaging a semiconductordevice is operated under a vacuum. The encapsulation area is defined bythe stencil, thus replacing the dam material. As a result, themanufacturing costs are reduced and the throughput is increased becausethe process is performed in one step.

[0035] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method for packaging a semiconductor device,wherein a chip is attached to a carrier and electrically coupled to thecarrier, comprising the steps of: providing a closed printing chamberhaving a baseplate; mounting the carrier and a stencil having a mesh insequence on the baseplate, wherein the carrier is located in the mesh;placing a preheated paste on the stencil; adjusting a pressure in theclosed printing chamber to a first pressure to perform a printing stepfor filling the mesh with paste and covering the carrier; adjusting thepressure in the closed printing chamber to a second pressure; andadjusting the pressure in the closed printing chamber to a thirdpressure to perform a scraping step for removing the redundant paste. 2.The method of claim 1, wherein the paste is heated by the baseplateduring the printing step and the scratching step.
 3. The method of claim1, wherein the paste is heated to a temperature of about 50 to 120° C.4. The method of claim 1, wherein the preheated temperature of the pasteis about 40 to 90° C.
 5. The method of claim 1, wherein the firstpressure is about 0.01 to 5 Torr.
 6. The method of claim 1, wherein thesecond pressure is about 350 to 1000 Torr when the viscosity of thepaste is about 200 to 300 Pa·s.
 7. The method of claim 1, wherein thesecond pressure is about 0.5 to 2 Kg/cm² when the viscosity of the pasteis about 600 to 1000 Pa·s.
 8. The method of claim 1, wherein the thirdpressure is about 5 to 20 Torr.
 9. A method for packaging asemiconductor device, wherein a plurality of chips is attached to aplurality of carriers, respectively, and electrically coupled to thecarriers, comprising the steps of: providing a closed printing chamberhaving a baseplate; mounting the carriers and a stencil having a mesh insequence on the baseplate, wherein the carriers are located in the mesh;placing a preheated paste on the stencil; adjusting a pressure in theclosed printing chamber to a first pressure to perform a printing stepfor filling the mesh with paste and covering the carriers; adjusting thepressure in the closed printing chamber to a second pressure; andadjusting the pressure in the closed printing chamber to a thirdpressure to perform a scraping step for removing the redundant paste.10. The method of claim 9, wherein the paste is heated by the baseplateduring the printing step and the scratching step.
 11. The method ofclaim 10, wherein the paste is heated to a temperature of about 50 to120° C.
 12. The method of claim 9, wherein the preheated temperature ofthe paste is about 40 to 90° C.
 13. The method of claim 9, wherein thefirst pressure is about 0.01 to 5 Torr.
 14. The method of claim 9,wherein the second pressure is about 350 to 1000 Torr when the viscosityof the paste is about 200 to 300 Pa·s.
 15. The method of claim 9,wherein the second pressure is about 0.5 to 2 Kg/cm² when the viscosityof the paste is about 600 to 1000 Pa·s.
 16. The method of claim 9,wherein the third pressure is about 5 to 20 Torr.
 17. The method ofclaim 9, further comprising the steps of: removing the stencil; curingthe paste; and splitting to form individual semiconductor packages. 18.An apparatus for packaging a semiconductor device, comprising: a closedprinting chamber; a pressure control system connected to the closedprinting chamber; a baseplate located in the closed printing chamber;and a paste source tank located in the closed printing chamber.
 19. Theapparatus of claim 18, wherein the baseplate includes a heating unit.20. The apparatus of claim 18, wherein the paste source tank includes avacuum chamber having a heating unit and an outlet opening.
 21. Anapparatus for packaging a semiconductor device comprising: a closedprinting chamber; a pressure control system connected to the closedprinting chamber; a baseplate having a heating unit located in theclosed printing chamber; and a paste source tank having a vacuum chamberlocated in the closed printing chamber, wherein the vacuum chamberincludes a heating unit and an outlet opening.